The Accelerator Localizing Cross Trays have divergent tungsten pins 1/16" and 3/32" in diameter x 1/2" long (0.16 and 0.24 x 1.27 cm). They are spaced 1 cm apart in four quadrants at isocenter. Every fifth pin is 3/32" (0.24 cm) diameter, which makes for easy counting. The small dots prevent any obscuring of the film viewing, yet allow easy measurements. The acrylic graticule fits into the metal tray so the graticule will not shift off center even if bumped.